Headlight.



J. A. ORANGE.

HEADLIGHT.

APPLICATION FILED was 9.:911.

Patented Mar. 5 1918.

2 SHEETS-SHEET Inventor John fl. Orange, u

His 'flttorneg.

l. A. ORANGE.

HEADLIGHT.

APPLICATION FILED JUNE 9. 1911.

Patented Mar. 5, 1918.

2 SHEETS-SHEET 2.

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UNITED STATES PATENT OFFICE.

JOHN A. ORANGE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

HEADLIGHT.

Specification of Letters Patent.

' Patented Mar. 5,1918.

Application filed June 9, 1917. Serial No. 173,754.

that no glare shall disturb an observer fac-- ing the headlight, so long as his eye is at or above the level of the same. This condition is not only necessar for the sake of safety, but is also prescribed by laws and ordi: nances in several States. A secondar object of my invention i to illuminate in li e manner, not only the roadbed, but also the sidewalks of streets or the ditches and footpaths on either side of roads.'

My bbjects are attained by a headlight window, molded in a novel manner, which closes the wide opening of an ordinary parabolic reflector, such as is commonly used, with the source of light in its focus. Generally speaking, my improved headlight window presents to the rays reflected upon it a large number of prisms of various'angularity, with their wedge ends or vertice directed upwardly. A mosaic comprising a large number of such suitably constructed prisms could be made to direct or bend downwardly all reflected elementary rays and if the incident rays were all paralle to the axis, which could only happen when the reflector is a practically correct paraboloid and the source of light closely approaches a point coincident with the focus of the reflector, the problem would be solved immediately by the use of a great number of like prisms, evenly distributed over the surface of the window, with their vertices directed upwardly. p

In practice the paraboloidal reflector sufliciently approaches mathematical accuracy, and the location of the source of light at the focus of the reflector offers no difficulty. But the source of light is far from approaching a mathematical oint; it has considerable extension, even w 1en a concentrated incandescent filament is employed as the source. Such concentrated filament may be regarded as and is-in effect a sphere of appreciable diameter. The consequence is that each element of the reflector receives a bundle of rays converging upon it from the source; it receives rays not onl from the direction of the focus but also f i'om points in advance of or behind the focus, and from points to the right and to theleft of the axis of the reflector. The bundle of rays, therefore is a cone, only the axial ray of which realiy comes from the direction of the focus.

This focal ray, as it may be called, is refiected by the paraboloid parallel to the axis of the latter, but all the otherreflected rays of the bundle diverge from the axis, and if the supposed great number of prisms on the window were alike and designed to direct the focal rays so as to strike the ground, say Y 300 feet ahead of the vehicle, they would not nerally, bend all incident rays downwar 1y into the desired field of illumination. Inasmuch as the requirement of ood distribution from the drivers stan oint calls particularly for good illumination of the parts of the ground farthest from the vehicle, it is necessary that the amount of downward bending at each and every part of the window be no more than sufiicient to produce a downward inclinationof all rays coming from the mirror defined as at least 1 in 100 or some similar standard determined by the desired range of illuminated ground surface.

It will be shown farther on that the bend: ing etfect of the window must vary from point to point if good distribution of light 1s to be secured, and while it is possible to make the different prisms which compose the supposed mosaic with different angles and to distribute them correctly over the window any attempt to do this by direct assembly would meet with great difiiculties and uncertainties. My invention is particularly directed to a regular distribution of such prisms in a manner which for pracplane, which may be the puteriuvlfi ffl liil) the window, if that surface is supposed to be flat. The arrangement is such that the angularity of the successive ring surfaces increases step by step as the rings approach the center of the window, in a manner dependent upon a number of factors, such as the size of the source of light, the focal length and the widest diameter of the reflector, the distance to which the illumination of the road is to be carried, and the index of refraction of the glass of which the window is made.

By the arrangement here broadly outlined, all rays issuing lfrom the headlight (other than those traveling direct from lamp to window) can be bent downwardly and the glare effect upon an eye stationed at or above the level of the top of the reflector is positively avoided, while the equally im-' portant matter of good distribution along the road is provided for.

But with this arrangement the width of the beam issuing from the headlight would not usuall be suflicient to cover even the road surface (honsidered transversely) to say nothing of curbs, ditches, etc.; therefore, I form the outer surface of my improved headlight window with vertical flutings, which may be circular or elliptical, and which operate to'bend the issuing rays to the right and to the left without affecting the downward bend of the rays, so that as wide a lateral range of illumination as is necessary is secured.

All this will more fully appear from the following detailed description, with reference to the accompanying drawing, in which:

Figure 1 is a diagram illustrating the aim and result of the invention; Fig. 2 is a View of the inner face of the improved headlight window, namely the face which is turned toward the source of light; Fig. 3 is a Vertical section of the window on the line aa of Fig. 2; Fig. 4 is an edge view of the window; Fig. 5 is a diagram showing upon a much exaggerated transverse scale the formation of the inner face of the headlight window, and Fig. 6 is a vertical section, similar to Fig. 3, illustrating diagrammati cally, on a much exaggerated scale the refraction of two beams of light. projected from the reflector upon one of the inclined rings formed on the inner face of the window.

Referring now particularly to Fig. 1, there is shown the outline 10 of a parabola which may be looked upon as a vertical section through the horizontal axis 11 of a paraboloidal reflector, the focus of which is indicated at 12, and the source of light at 13, by a'circle. The window which is at right angles to the axis of the reflector, is indicated diagrammatically at 14.- without reference to its peculiar formation. The source of light extends around the focus somewhat in the form of a'sphere, having a diameter of appreciable size. This source of light, which may be a concentrated incandescent filament, projects raysin all directions upon the surface of the paraboloid and these rays'are reflected from that surface against the window through which they pass into the outside field of illumination, after suffering refractions at the two faces of the window. Each point of the paraboloid receives a bundle of rays coming from many parts of the light source; it is a cone the base of which is in the source and the vertex is at a point of the paraboloid. Considering here merely the vertical section of the paraboloid, one of the points of the parabola 10, say the point 15, receives a flat triangular bundle of elementary rays, one of which, 16, indicated by a dotted line, comes from the direction of the focus, while the marginal rays 17-18 come from the ends of a diameter of the source. The triangle is therefore an isosceles triangle and these rays are reflected at the point 15, again in the form of an isosceles triangle, against the window 14, these reflectedrays being indicated by the lines 16, 17 and 18. The ray 16' is the reflection of the ray 16 which strikes the point 15 from the direction of the focus. Therefore, the reflected ray 16 is parallel to the axis 11; it is a horizontal ray, while the reflected ray 17' diverges upwardly and the reflected ray 18' diverges downwardly from the horizontal, and there are, of course, innumerable other rays between 17' and 18'. All these rays falling upon the window are there received upon one or more ring surfaces and are refracted twice, and the inner surface of the window is so shaped, as will appear farther on, that all these rays after passing through the window issue into the field of illumination as downwardly diverted rays 17", 16 and 18"; and the same thing is true of all reflected rays intermediate between 17 and 18'.

This is one of the aims of the invention, that is to say, all rays reflected from any point of the paraboloid are intended to issue into the field of illumination downwardly inclined. The field of illumination is the roadbed and consequently this roadbed will be illuminated from a point in advance of but near the headlight to a suitable distance, say about 300 feet in such manner that the eye of an observer at or above the horizontal plane passed through the highest point of the reflector will receive no reflected and then refracted light, or practically no such light. What has here been said of the bundle of rays falling upon the point 15, is true of the light falling upon all other points of the reflector, such as 15. and 15", with this difference, however, that as the points of the reflector recede from the axis 11 more and more the angularity of the incident beams of light becomes less and less, as indicated in the drawing, and in order that the upper marginal rays of these beams and all other rays of each bundle issue similarly, the window must be shaped differently, step by step, from the center outwardly. \Vhat has here been said with respect to elements of the reflector included in a vertical axial section applies equally'to corresponding elements otherwise located but it is not possible to represent such cases intelligibly on a plane diagram.

The inner face of the window is shown in Figs. 2 and 3, shaped as a series of concentric rings, each ring having a flat face and, with the exception of the outermost ring, the face of each ring forms an angle with an imaginary vertical datum plane which is assumed to be parallel tothe plane of the outer surface of the window. The angle thus formed between these rings and the datum plane increases from ring to ring as these approach the center of the window. The outermost ring 19 is parallel with the datum plane, or with the outer face 20 of the window, this outer face being temporarily supposed to be fiat. ring has no optical function; it merely serves as a rim for mounting the window against an appropriate structure at the wide opening of the reflector. The second ring 21 forms a small altitude angle with the imaginary datum plane and is at its inner circumference suddenly stepped on tothe third ring 22, which forms a somewhat larger angle with the imaginary datum plane. This ring a ain is at its inner circumference steppe on to the fourth'ring 23 which forms a still larger angle with the imaginary datum plane, and so forth until the center of the window is reached, which has the form of a disk 36 and which forms the largest angle with the datum plane.

This is articularly clearl illustrated in Fig. 5 whlch represents a view like that of Fig. 3 but showing the window upon a larger scale and with its transverse dimensions very largely exaggerated for the sake of clearness. In this diagrammatic vertical section the datum plane to which the successive rings are referred' is indicatedby the line XY. It will be seen that the first ring 19 is parallel tothe datum plane, while the flat surface of the second ring21- forms a small altitude angle with that plane, intersecting the same at the line Z, which corresponds to the horizontal diameter of the window. Therefore, as here shown, the second ring is at the upper end of its diametendepressed with reference to the datum plane XY and at the lower end of its diameter it is elevated above the datum plane. The face of the third ring 22 is reached by a sudden step fromthe second ring 21 and the face of this ring 22 forms, as is clearly indicated This outermost in Fig. 5 a greater altitude angle with the datum plane XY than does the ring 21. The same thing is true as respects the transition from the third ring to the fourth ring 23, which again forms a larger altitude angle than ring 22 with the datum plane. And in the same manner every successive inner ring 24, 25, 26, etc., is reached from the next preceding outer ring and forms an ever greater altitude angle with the datum plane, until the central element of the Window, the circular disk 35, is reached, which forms the greatest altitude angle with the datum plane. It will now be understood that the face of each ring in combination with the outer flat surface of the window is in efi'ect a collection of a very large number of prisms of the same altitudinal angularity, the angularity of the prisms increasing from ring to ring toward the center so that rays falling upon these prismrings will be refracted in like degree from any part of the same ring, but in different degree from every other ring.

That the bundle of reflected rays falling upon different parts of the same ring are refracted in like manner and issue into the field of illumination with the corresponding elementary rays parallel to each other, can readily be seen by contemplation of Fig. 6 which shows a partial vertical section upon a largely exaggerated scale of the window by a plane either coincident with that marked in Fig. 2, by w-a or by a plane parallel thereto. The ring here shown may be any one of those indicated in Figs. 2-3-5, 1

and in order to fix ideas it may be assumed to be the ring 30. A bundle of reflected rays falling upon the upper part of ring 30 is here represented by the lines 3637-38, the central ray 86 of the bundle is, as in Fig. 1, supposed to be parallel to the axis of the reflector while the upper marginal my 37 is inclined upwardly and the lower marginal ray 38 is inclined downwardly, with respect to the axis. The angularity of the ring 30 must be such that with a given index of -with the datum plane, or what is the same thing, with the supposed flat outer surface of the window, there is no reason why like bundles of rays falling upon these parts, respectively, should be refracted differently. Consequently the rays 37' and 40' will be parallel to each other, -the rays 36' and 39 will in turn be parallel to each other, and

the same thing is true of the rays 38 and 41', respectively, and with all intermediate rays, and all of them will be inclined downwardly.

While each part of any given ring will as here shown refract bundles of rays directed upon the same by the reflector to the same extent, the refraction will be different for the different rings and will increase from the outer to the inner rings, step by step, so that each successive inner ring will bend the rays' more and more downwardly, as illustrated in Fig. 1. It will now be understood that the angularity of the rings formed on the inner face of the window can be so chosen that the rays of least inclination from each and every ring will reach the roadbed at the desired distance, say 300 feet, in advance of the headlight. The other rays from each ring will reach the ground at nearer points and it is evident that the inward extent of the illuminated zone will be of difierent length for the different rings, being least for the outer ring and greatest for the central disk.

It is this peculiar disposition which secures good longitudinal distribution of light in addition to freedom from glare.

Freedom from glare alone, without regard to range of illumination and proper distribution of the light, is easily secured by simply giving to the ordinary headlight as a whole a downward inclination. Such dip- P resorted to with the result that a short length of road was brightly illuminated with utter darkness beyond and also immediately in front of the vehicle. With my improved headlight window the range of illumination which the window is toserve can be,determined and any desired distribution of the light can be secured.

It is also practicable and within my invention to so modify the construction of the window as to enable the operator to lengthen and shorten the range of illumination within wide limits without affecting.

the proper distribution of light. 'To secure thisresult it 'is only necessary to so choose the angularity of the prism rings that the upper marginal rays of each bundle of light issue parallel to the axis of the reflector; a downward dip of the headlight by a few degrees, more or less, then determines the range of illumination, while the proper distribution of light due to the different angularities of the rings remains undisturbed.

The direct light from the source will be refracted by the window in a variety of degrees according to the different rings which it primarily strikes, and some of this light would, if no other precaution were taken, .reach the eye of the observer staof the headlighthas sometimes been tioned above the level of the headlight. There, would, in practice be little if any inconvenience resulting from such light, because it is generally too faint to produce a glare, particularly at some distance in advance of the headlight; but in order to prevent the direct light from issuing above the level of the headlightthe familiar prac-' tice of blinding or dimming a limited upper, forward portion of the bulb of the mean descent lamp, if such is used as the source, may be resorted to. This is a common practice, and a similar practice is also available For the attainment of the main object of my invention the ring formation of one,

preferably the inner surface of the window is essential, while the outer surface of the window may just as well be flat. But for the attainment of the secondary object of my invention, which is to spread thelight to the right and to the left so as to illuminate a considerable width of the roadbed and -en to the sidewalks of streets or the ditches or pathways along roads, the outer face of the window is fluted vertically as indicated at 42 in Figs. 3-45 and by the s aced vertical dotted lines in Fig. 1. These utings may be either circular or elliptical, according to the spread of light desired, and they do not interfere with the downward bend of the rays issuing from the window. Such or similar flutings have heretofore been used in headlight windows of other description, but they are of special advantage in combination with the prism rings of my improved headlight window.

It is obvious that'it is of no consequence whether the surface of the window with the ring formation faces the source of light and the flat or fluted surface the road, as was assumed in the foregoing description, or whether the arrangement is reversed. The optical effect is the same in either case, but the flat or fluted face will preferably be used as the outer one, because it is easier to cleanse it than the face with the ring formation.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A headlight window. formed with plane, concentric ring surfaces, angularly disposed with reference to each other.

resent-ea 2. A headlight window formed with plane, concentric ring surfaces, angularly disposed with reference to each other and intersecting in a line common to all.

3. A headlight window formed with plane, concentric ring surfaces, angularly disposed with reference to each other and intersecting in a line coincident with a diameter of each ring.

4. A headlight window formed with plane, concentric ring surfaces, angularly disposed with reference to a common datum plane and to each other, the angularity of each ring surface with respect to the datum plane being greater than that of the next preceding outer one and all these planes intersecting in a line coincident with a diameter of each ring.

5. A headlight window formed on one face with plane, concentric ring surfaces, angularly disposed with reference to each other and intersecting in a line common to all, and at the other face formed with flutings extending at right angles to the line of intersection of the ring surfaces.

6. A headlight Wil'ldOW formed on one face with plane, concentric r ng surfaces, an-

gnlarly disposed with reference to each,

other and intersecting in-a line coincident with a diameter of each ring, and at the other face formed with flutings extending at right angles to the said diameters.

7. A headlight comprising a paraboloidal reflector, a source of light of sensible size at and about the focus of the reflector, and a window across the reflector opening formed on one face with plane, concentric ring surfaces angularly disposed with reference to each other.

8. A headlight comprising a paraboloidal reflector, a source of light of sensible size at and about the focus of the reflector, and

a window across the reflector opening formed with plane, concentric ring surfaces angularly disposed with reference to each other and intersecting in a line coincident with a diameter of each ring.

9. A headlight comprising a paraboloidal reflector, a source of light of sensible size at and about the focus of the reflector, and a window across the reflector opening formed with plane, concentric ring surfaces angularly disposed with reference to a common datum plane and to each other, the angularity of each ring surface with respect to the datum plane being greater than that of the next preceding outer one.

10. A headlight comprising a paraboloidal reflector, with its axis substantially horizontally disposed, a source of light of sensible size at and about the focus of the reflector, and a window substantially at. right angles across the reflector opening formed with plane, concentric ring surfaces angular-1y disposed with reference to each other and intersecting in a line coincident with the horizontal diameter of each ring,

11. A headlight comprising a paraboloidal reflector, with its axis substantially horizontally disposed, a source of light of sensible size at and about the focus of the reflector, and a window substantially at right angles across the reflector opening formed with plane, concentric ring surfaces angularly disposed with reference to a common datum plane and to each other and intersecting in a line coincident with the horizontal diameter of each ring, the singularity of 'each ring surface with respect to the datum plane being greater than that of the next preceding outer one.

In witness whereof, I have hereunto set my hand this 8th day of June, 1917.

JOHN A, ORANGE. 

